7-/aS  .5-  i^O 


s 

CONNECTICUT  ,E^^S< 

Agricultural  Experiment  Station  "^  °  '  ^^ 

NEW    HAVEN,    CONN. 


BULLETIN   190,  JANUARY,  1916 


ENTOMOLOGICAL  SERIES,   No.   21 


INSECTS  attacking  CABBAGE  AND  ALLIED 
CROPS  IN  CONNECTICUT 


Fig.  I.     Cabbage  Field  showing  damage  by  Cabbage 
Maggot. 


Officers  and  Staff. 

Insects    attacking    Cabbage  and 

allied  Crops  in  Connecticut ..  .  3 

Cabbage  Root  Maggot 3 

Imported  Cabbage  Worm  or  But- 
terfly    9 

Potherb  Butterfly 11 

Southern  Cabbage  Buttertl}' 11 

Cabbage  Looper 12 


CONTENTS. 

Page 


Page 

Cabbage  Aphis 14 

Cabbage  Plutella 15 

Zebra  Caterpillar 16 

Harlequin  Cabbage  Bug 17 

Cutworms 18 

Wireworms 20 

Cabbage  Snakes 20 

Cultural    Practices 22 

Literature 22 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Con- 
necticut who  apply  for  them,  and  to  others  as  far  as  the  editions 
permit. 


CONNECTICUT  AGRICULTURAL  EXPERIMENT  STATION. 

OFFICERS  AND  STAFF. 


BOARD  OF  CONTROL. 

His  Excellency,  Marcus  H.  Holcomb,  ex-officio,  President. 

Prof.  H.  W.  Conn,  Vice  President  Middletown 

George  A.  Hopson,  Secretary Wallingf ord 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven 

Joseph  W.  Alsop  Avon 

Wilson  H.  Lee  Orange 

Frank  H.  Stadtmueller   Elmwood 

James  H.  Webb  Hamden 


Administration.  E.    H.   Jenkins,   Ph.D.,   Director   and   Treasurer. 

Miss  V.  E.   Cole,   Librarian  and  Stenographer. 
Miss  L.  M.  Brautlecht,  Bookkeeper  and  Stenographer. 
William  Veitch,  In  charge  of  Buildings  and  Grounds. 

Chemistry. 

Analytical  Laboratory.  John   Phillips   Street,   M.S.,    Chemist   in   Charge. 
E.  Monroe  Bailey,  Ph.D.,  C.  B.  Morison,  B.S., 
C.  E.  Shepaed,  G.  L.  Davis,  Assistants. 
Hugo  Lange,  Laboratory  Helper. 
V.   L.   Churchill,    Sampling  Agent. 
Miss   E.   B.  Whittlesey,  Stenographer. 


Proteid  Research. 


Botany. 


Entomology. 


T.   B.   Osborne,  Ph.D.,   Chemist  in  Charge. 
Miss  E.   L.  Ferry,   M.S.,  Assistant. 

G.  P.  Clinton,  Sc.D.,  Botanist. 
E.  M.  Stoddard,  B.S.,  Assistant  Botanist. 
Miss  E.  B.  Whittlesey,  Herbarium  Assistant. 
G.  E.  Graham,   General  Assistant. 

W.   E.   Briti'ON,   Ph.D.,  Entomologist;    State  Entomolgist. 
B.  H.  Walden,  B.Agr.,  First  Assistant. 
Q.  S.  Lowry,  B.Sc,  I.  W.  Davis,  B.Sc,  I 
M.  p.  Zappe,  B.S.,  ' 

Miss  G.  A.   Foote,  B.A.,  Stenographer. 


Assistants. 


Forestry. 


Plant  Breeding 


Vegetable  Growing. 


Walter  O.  Filley,  Forester;    also  State  Forester 

and  State  Forest  Fire   Warden. 
A.   E.  Moss,   M.F.,  Assistant  Station  Forester. 
Miss  E.  L.  Avery,  Stenographer. 

Donald  F.  Jones,  B.S.,  Plant  Breeder. 
C.  D.  HuBBELL,  Assistant. 

Howard  F.  Huber,  B.S. 


INSECTS  ATTACKING  CABBAGE  AND  ALLIED  CROPS 
IN  CONNECTICUT 

By  W.  E.  Brixton  and  Ouincy  S.  Lowry. 

The  object  of  this  bulletin  is  to  place  in  the  hands  of  vegetable 
growers  a  single  publication  giving  information  about  the  insects 
attacking  cabbage,  cauliflower,  and  allied  plants  in  Connecticut. 
The  subject  matter  is  not  entirely  a  compilation  as  the  senior 
author  has  made  observations  on  the  insects  in  the  state  for 
many  years,  and  for  the  past  two  seasons  definite  experimental 
work  has  been  carried  on  by  the  junior  author  to  control  the 
cabbage  root  maggot. 

Cabbage  Root  Maggot:   Phorbia  brassicce  Bouche 

The  most  important  insect  pest  of  early  cabbages  in  Connecti- 
cut is  the  root  maggot,  which  attacks  not  onl}-  cabbage,  but  also 
other  allied  plants  such  as  cauliflower,  turnip  and  radish. 

This  insect  is  a  native  of  Europe,  and  was  introduced  into 
this  country  probably  by  accident,  making  its  first  appearance  in 
Massachusetts  more  than  seventy  years  ago.  According  to  pub- 
lished statements  it  has  now  spread  throughout  the  United  States 
and  Canada,  and  caused  injury  wherever  its  food  plants  are 
grown.  Some  entomologists,  however,  consider  this  questionable 
and  regard  another  species,  P.  fusciceps  Zett.,  which  is  a  general 
feeder,  as  responsible  for  tlie  injury  in  the  Southern  Atlantic 
states.  Be  this  as  it  may,  the  insect  surely  causes  severe  damage 
in  the  northern  and  eastern  states  and  seems  to  be  on  the  increase, 
though  Dr.  J.  Fletcher,  as  early  as  1885,  reported  it  as  destroy- 
ing from  25  to  75  per  cent,  of  the  cauliflower  plants  in  Canada. 
The  damage  to  early  cabbages  was  especially  serious  in  Con- 
necticut in  191 5.  The  maggots  feed  upon  and  tunnel  in  the  main 
stem  and  larger  roots  just  below  the  surface  of  the  ground  as 
shown  in  figure  2,  greatly  reducing  the  vitality  of  the  plants  and 
often  causing  them  to  wilt  and  die.  Plants  which  have  been 
moderately  or  severely  injured  will  not  recover  and  make  satis- 
factory heads,  even  though  the  maggots  are  killed.     This  insect 


4  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

seldom   injures    cabbages   late    in   the    season   but   often   causes 
serious  injury  to  turnips  and  radishes. 

Description  and  Life  History. — The  maggots  are  the  larvae 
of  a  small,  two-winged  fly  which  lays  eggs  on  or  near  the  stem 
of  the  plant,  usually  just  beneath  the  surface  of  the  ground  late 


Fig.  2.     Young  Cabbage  Plant  showing  Maggots  on 
outside  of  Stem.     Natural  size. 


in  April  or  early  in  May.  There  are  at  least  three  and  possibly 
four  broods  each  year.  The  second  brood  appears  about  the 
middle  of  June,  but  it  is  only  the  first  brood  that  seems  to  cause 
serious  damage  to  cabbage  and  cauliflower  crops. 

Egg. — Pure  white,  oval,  about  i  mm.  or  1/25  of  an  inch  in 
length.      Though    eggs    are    deposited    separately,    each    female 


CABBAGE    ROOT    MAGGOT.  5 

averages  between  50  and  60  eggs.  These  eggs  hatch  in  from 
three  to  five  days  according  to  chmatic  conditions. 

Larva. — When  fully  grown  the  maggot  is  about  8  mm.  or  1/3 
of  an  inch  long  and  yellowish  white  in  color.  It  has  no  legs 
and  is  quite  helpless :  if  it  hatches  far  from  its  food  plant  it  is 
sure  to  perish.  It  cannot  bite  but  its  mouth-parts  enable  it  to 
scrape  away  the  tissues  of  the  host  plant,  which  soon  begins  to 
decay,  thus  making  it  easier  for  the  maggots  to  penetrate.  From 
three  to  four  weeks  are  required  for  the  maggot  to  reach  maturity. 

Pupa. — AMien  mature  the  larva  or  maggot  leaves  its  host  plant, 
descends  an  inch  or  more  into  the  soil  and  transforms  to  the  pupa 
stage  by  utilizing  its  outer  skin  for  a  shell  or  puparium  after  the 


I'iG.  3.     Puparia  and  Adult  of  llic  Cabbage  ]Maggot.     Enlarged. 

manner  of  flies.  The  brown  pupae  are  abundant  in  Connecticut 
about  the  middle  of  June.  This  stage  usually  requires  about  two 
weeks,  though  with  the  late  fall  brood  it  lasts  through  the  winter, 
the  pupae  being  found  as  late  as  May  7th  the  following  spring. 

Adult. — The  two-winged  fly  is  gray  with  thorax  and  abdomen 
more  or  less  irregularly  marked  with  black.  It  somewhat  resem- 
bles the  common  house  fly,  though  smaller,  and  the  female  is 
lighter  than  the  male  and  has  fewer  distinctive  characters.  The 
male  has  a  tuft  of  bristles  on  the  under  side  of  each  femur  which 
distinguishes  it  from  allied  species.  Adults  are  known  to  pass 
the  winter  in  stubble  in  the  field  and  in  similar  places  where  they 
can  find  protection.    Adult  and  puparia  are  shown  in  figure  3. 

Natural  Enemies. — A  number  of  predaceous  and  parasitic 
insects  are  known  to  attack  the  cabbage  root  maggot.     A  small 


6  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

spider,  Trombidium,  sucks  the  eggs.  Some  of  the  rove  beetles 
(family  Staphylinidse)  devour  large  numbers  of  maggots. 
Several  four-winged  flies  are  known  to  be  parasitic  on  the  cab- 
bage maggot,  and  in  Minnesota  a  few  years  ago  three  new 
species,  one  a  serphoidid,  Loxotropa  pcgomyicc  Brues,  and  two 


Fig.  4.     Plant  Protected  b}-  Tarred  Paper  Disk. 


ichneumonids,  Mcsocrina  pegomyice  Brues  and  ApJicureta  pego- 
myice  Brues,  were  reared  from  the  puparia.* 

Control  Methods. — The  most  efifective  and  economic  method 
of  control  is  to  place  around  the  stem  of  each  plant,  soon  after 
setting,  a  disk  of  tarred  paper  as  shown  in  figure  4.    These  disks 


*  Report  of  Minnesota  State  Entomologist  for  1907-1908,  page  192. 


CABBAGE    ROOT    MAGGOT.  7 

may  be  purchased  from  Hirsch  Bros.,  2257  Metropolitan  Ave., 
Middle  Village,  N.  Y. ;  Smith  Bros.,  Green  Bay,  Wis.;  A.  B. 
Cowles,  25  South  Water  St.,  Rochester,  N.  Y.,  or  they  can  be 
cut  at  home  as  shown  in  figures  5  and  6. 

In  our  experiments  at  the  Station  Farm,  Mt.  Carmel,  in  1915, 
the  insect  was  very  abundant  and  caused  a  loss  of  23.3  per  cent, 
of  the  untreated  plants,  though  close  beside  them  where  the 
tarred  paper  disks  were  applied  there  was  a  loss  of  only  4.4  per 


Fig.  5.     Tool  and  Device  for  Cutting  Disks. 


cent.  The  carbolic  acid  emulsion  treatment  permitted  a  loss  of 
only  6  per  cent.  The  difference  is  shown  in  figure  7.  Similar 
results  have  been  obtained  in  preceding  tests. 

Perhaps  the  second  most  effective  control  method  is  to  pour 
into  a  surface  depression  around  the  stem  of  each  plant  about 
three  fluid  ounces  of  crude  carbolic  acid  emulsion  made  after  the 
following  formula: 

Hard  soap,  i  lb.,  or  soft  soap,  i  qt. 
Boiling  water,  i  gal. 
Crude  carbolic  acid,  i  pt. 


CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 


Fig.  6.     Wood  Form  for  cutting  Hexagonal  Disks. 

Dissolve  the  soap  in  the  boiHiig  water,  add  the  acid  and  churn 
as  in  making  kerosene  emulsion.  This  mixture  thickens  on  cool- 
ing and  should  be  diluted  with  30  times  its  bulk  of  water  before 
using. 


Fig.  7.     Plants  at  left  were  protected  bj^  Tarred  Paper  Disks;    injury  less 

than  5  per  cent.     Those  at  right  were  untreated ;    nearly 

one-third  were  injured. 


Clean  culture,  destruction  of  infested  stumps  and  other  rub- 
bish, and  crop  rotation  are  important  practices  in  controlling  the 
cabbage  maggot. 


imported  cabbage  worm.  9 

The  Imported  Cabbage  Worm  or  Butterfly. 

Pontia   (Pieris)   rapce  Linn. 

This  is  the  larva  of  the  common  white  cabbage  butterfly,  a 
well-known  European  pest  which  was  introduced  into  Canada 
about  i860,  and  has  since  spread  nearly  all  over  the  United 
States,  largely  supplanting  the  native  species.  There  are  usually 
three   annual   generations   in  the  north,   and  five   or   six   in  the 


Fig.  8.     Imported  Cabbage  Worms.     Natural  size. 


southern  states.  The  entire  life  cycle  requires  from  three  to 
five  weeks.  The  larvae  injure  the  plants  by  feeding  on  the  outer 
leaves,  often  stripping  them. 

Description  and  Life  History. — This  is  one  of  the  first  butter- 
flies to  appear  in  spring,  and  is  often  seen  in  Connecticut  on 
warm  days  in  March. 

Egg. — Eggs  are  laid  singly  on  the  under  side  of  the  leaf  of 
any  available  plant  of  the  cabbage  family  (Criiciferae).  They 
are  fastened  to  the  leaf  by  one  end,  and  are  about  i  mm.  or  one- 


lO  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

twenty-fifth  of  an  inch  in  length,  hght  yellow,  bullet-shaped, 
sculptured  with  prominent  longitudinal  ridges  and  transverse 
striae.     From  4  to  8  days  are  required  for  hatching. 

Larva. — About  31  mm.  or  one  and  one-fourth  inches  long  when 
full  grown,  velvety  green,  with  a  paler  yellowish  stripe  along 
the  back,  and  row  of  spots  along  each  side.  It  moves  sluggishly, 
and  feeds  ravenously  on  the  outer  or  loose  leaves.  From  ten 
to  fourteen  days  are  passed  in  this  stage,  which  is  shown  in 
figure  8. 

Pupa. — The  pupa  or  chrysalis  is  about  three-fourths  of  an  inch 
long,  at  first  pale  green  but  later  turning  brown,  marked  with 
small  black  spots.  It  is  suspended  horizontally  by  silken  threads, 
sometimes  to  its  food  plant,  but  often  under  fence  rails,  edges 


Fig.  9.     Chrysalis  of  Imported 
Cabbage  Butterfly.    Natural 


Fig.  10.     Imported  Cabbage  Butterfly,  Female 
at  left.     Natural  size. 


of  clapboards  and  shingles  on  buildings,  etc.  With  the  early 
broods  from  seven  to  fourteen  days  is  passed  as  a  chrysalis,  but 
the  late  fall  brood  passes  the  winter  in  this  condition.  Shown  in 
figure  9. 

Adult. — The  butterfly  has  a  wing-expanse  of  about  two  inches. 
Wings  yellowish  white,  marked  with  black  at  the  tips.  The 
female  has  two  circular  black  spots  on  each  fore  wing;  the 
male  has  only  one.  Both  sexes  have  a  black  spot  on  the  anterior 
margin  of  the  rear  wing.  Head,  antennae  and  upper  side  of 
body  are  nearly  black.  Under  side  of  body  and  legs  are  yellowish 
white.    Shown  in  figure  10. 

Natural  Enemies. — A  small  four-winged  fly  or  braconid, 
Apanteles  glomeratus  Linn.,  is  the  most  common  parasite  and  was 


POTHERB    BUTTERFLY.  II 

quite  abundant  at  the  Station  field  at  Mt.  Carmel  in  191 5. 
Another  common  parasite  is  a  minute  chalcid  fly,  Pteromalus 
piiparum  Linn.  Various  wasps,  especially  the  common  wasp, 
Polistes  pallipcs  LeP.,  prey  upon  the  larvae. 

Control  Methods. — Cabbage  growers  usually  spray  or  dust 
their  plants  with  lead  arsenate  and  it  is  perfectly  safe  before  the 
plants  are  headed.  When  nearly  ready  to  harvest,  it  is  advisable 
to  dust  the  plants  with  insect  powder  (Pyrethrum)  or  some  other 
fine  dust  applied  with  a  blower  or  powder  gun.  Water  heated 
to  a  temperature  of  130°  F.  is  said  to  kill  all  worms  with  which 
it  comes  in  contact  without  injuring  the  plants. 

The  Potherb  Butterfly. 
Pontia  napi  Linn. 

This  native  species  occurs  in  Canada  and  in  the  northeastern 
United  States,  and  was  formerly  the  common  cabbage  worm, 
but  has  now  been  almost  entirely  replaced  in  cabbage  fields  by 
the  imported  cabbage  worm,  P.  rapes.  The  larva  resembles  that 
of  the  imported  cabbage  worm  but  is  about  the  same  color  as  the 
cabbage  leaf  and  usually  feeds  upon  the  under  side,  leaving  a 
network  of  veins. 

The  adult  does  not  appear  as  early  in  spring  and  its  wings  are 
nearly  all  white  without  the  black  spots.  It  now  feeds  chiefly 
on  native  vegetation. 

The  remedies  used  against  the  imported  cabbage  worm  will 
also  control  this  species. 

The  Southern  or  Checkered  Cabbage  Butterfly. 
Pontia  protodice  Boisdv. 

This  butterfly  is  a  native  of  the  United  States  and  is  much 
more  abundant  in  the  southern  states  than  in  the  north. 
Though  adults  are  frequently  seen  and  taken  in  Connecticut,  we 
have  not  observed  the  larvae  injuring  cabbages  here.  Farther 
south  this  species  was  considered  a  serious  pest  of  cabbage  plants 
before  the  advent  of  the  imported  cabbage  worm  in  the  United 
States,  the  latter  having  largely  replaced  it  as  a  pest. 

The  habits  of  this  species  and  the  control  methods  used  against 
it  are  practically  the  same  as  given  above  for  P.  rapcc. 

The  egg  and  chrysalis  are  very  similar  to  that  species,  but  the 
larva  differs  in  having  two  pale  yellow  stripes  along  each  side. 


12  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    IQO. 

The  adult  is  also  larger,  the  male  resembling  that  of  the 
imported  cabbage  worm  but  with  additional  spots  on  the  fore 
wings,  and  the  female  is  heavily  marked  with  black  on  both 
front  and  rear  wings,  as  shown  in  figure  ii. 


f. 

_^^ 

.. 

\ 

1 

^mm 

B>^p| 

B^^^^JS 

C^H 

a'  '^ 

^     f .  MH 

^«""^ 

^td/ 

a^:M 

L 

'^ 

-■=^^^H 

P' 

r 

^JHr*^ 

"^1 

ii 

^ 

k 

i 

1 

IH 

Fig.  II.     The  Southern  or  Checkered  Cabbage  Butterfly,  Female  at  left. 

Natural  size. 


The  Cabbage  Looper  or  Cabbage  Plusia. 
x4utographa  hrassicce  Riley. 

As  a  pest,  the  cabbage  looper  ranks  next  to  the  imported  cab- 
bage worm  and  in  certain  seasons  in  some  localities  may  even 
do  greater  damage.  The  name  comes  from  the  looping  habits 
of  its  larva,  due  to  the  absence  of  pro-legs  on  the  third  and 
fourth  abdominal  segments,  as  is  the  case  with  the  measuring 
worms. 

This  insect  is  well  distributed  east  of  the  Rocky  Mountains, 
but  is  far  more  destructive  in  the  southern  states,  though  it 
is  injurious  in  the  north.  In  Connecticut  there  are  at  least  two 
broods  each  year,  while  in  Florida  six  broods  have  been  recorded. 
The  larva  feeds  on  nearly  all  cruciferous  plants  and  when  abund- 
ant often  injures  other  vegetables,  and  in  late  fall  occasionally 
attacks  plants  in  the  greenhouse. 

Description  and  Life  History. — This  insect  does  not  appear 
as  early  in  the  season  as  the  imported  cabbage  worm,  and  the 
larva  may  be  recognized  by  its  smooth  skin,  body  tapering 
towards  the  head,  its  light  green  color  and  looping  habit.    Instead 


CABBAGE    LOOPER. 


^3 


of  feeding  wholly  on  the  outer  leaves,  the  larvae  often  go  deep 
into  the  head. 

Egg. — The  egg  is  about  the  size  of  a  mustard  seed,  convex 
and  pale  green,  and  is  laid  singly,  usually  on  the  upper,  though 
occasionally  on  the  under  side  of  the  leaf. 

Larva. — The  full  grown  larva  is  from  one  to  one  and  three- 
eighths  inches  long,  pale  green,  indistinctly  and  longitudinally 
striped  with  white.  It  is  narrowest  at  the  head  and  gradually 
broadens  toward  the  distal  extremity.  The  larval  period  varies 
from  two  to  four  weeks. 


/ 


Fig.  12.     Cabbage  Looper,  A.  brassicce,  showing  Adult,  Larva, 

and  Pupa  Stages.    Natural  size.     (x\fter  Chittenden, 

Bureau  of  Entomology,  Bull.  3;^,  U.  S.  D.  A.) 


Pupa. — The  pupa  or  chrysalis  is  formed  within  a  white  silken 
cocoon  on  the  leaves  of  the  host  plant.  The  duration  of  the 
pupal  stage  varies  from  one  week  in  summer  to  three  weeks  in 
fall,  and  the  last  seasonal  brood  winters  as  a  chrysalis. 

Adult. — The  adult  is  a  noctuid  moth  with  grayish  brown  fore- 
wings  marked  wath  white.  It  has  a  wing-expanse  of  about  one 
and  one-half  inches  and  each  fore  wing  is  ornamented  near  the 
center  with  a  silver  dot  and  U-shaped  mark.  The  rear  wings 
are  of  lighter  brown  with  darker  scalloped  margins. 

Larva,  pupa  and  adult  moth  are  shown  in  figure  12. 


14  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

Control  Methods. — As  a  rule  the  methods  employed  against 
the  other  cabbage  worms  will  control  this  species  but  on  account 
of  its  habit  of  eating'  into  the  heads  arsenical  poisons  should 
not  be  used  on  headed  plants.  The  cabbage  looper  is  apparently 
not  as  susceptible  to  dry  powders  as  is  the  imported  cabbage 
worm. 

The  Cabbage  Aphis  or  Plant  Louse. 

Aphis  hrassicce  Linn. 

The  cabbage  aphis  is  another  serious  pest  brought  to  this 
country  from  Europe,  probably  on  cabbage,  and  has  since  spread 


Fig.  13.     Cabbage  Aphis  on  Leaf.     Natural  size. 

rapidly  throughout  the  United  States.  It  is  present  and  usually 
abundant  every  year  in  Connecticut,  though  affected  considerably 
by  atmospheric  conditions.  It  is  usually  found  on  the  under  side 
of  the  leaves  where  it  sucks  the  sap,  often  causing  great  damage 
when  abundant.    It  is  even  a  more  serious  pest  farther  south. 

Description  and  Life  History. — This  insect  appears  here  in 
June,  and  like  most  plant  lice,  several  generations  of  winged  and 
wingless  females  are  produced  which  bring  forth  living  young. 
On  the  approach  of  cold  weather  a  true  sexual  generation  is 
produced  and  the  females  lay  eggs  to  carry  the  species  through 
the  winter. 

The  young  nymph  is  pale  green  with  black  legs  and  antennae. 
The  mature  forms  are  yellowish  green  with  black  head  and  eyes 


CABBAGE    APHIS.  I  5 

and  dark  cornicles  or  honey  tubes.  Except  for  the  wings,  the 
winged  and  wingless  forms  resemble  each  other. 

Instead  of  occurring  individually  on  the  leaves  as  is  the  case 
with  some  plant  lice,  the  cabbage  aphis  usually  occurs  in  large 
colonies,  often  covering  considerable  leaf  surface  on  badly 
infested  plants.  The  wax  exudation  gives  the  colony  a  bluish 
bloom  and  interferes  somewhat  with  the  application  of  insecti- 
cides.   This  insect  is  shown  in  figure  13. 

Natural  Enemies. — Lady  beetles,  chrysopid,  and  syrphid 
larvae,  and  many  minute,  four-winged  parasitic  flies  help  to  hold 
the  cabbage  aphis  in  check. 

Control  Methods. — The  nicotine  solution  known  as  "black 
leaf  40,"  one  teaspoonful  in  a  gallon  of  water,  with  a  little  soap 
added,  and  sprayed  upon  the  plants,  proved  effective  and  satis- 
factory in  destroying  this  aphid  in  our  experiments  at  Mt. 
Carmel.  On  account  of  the  wax  secretion,  it  is  necessary  to  add 
the  soap.  Any  mixture  of  tobacco  and  laundry  or  whale-oil  soap, 
or  even  the  soap  alone,  will  probably  prove  successful  if  it  con- 
tains at  least  one  pound  of  soap  to  eight  gallons  of  water.  In 
any  attempt  to  control  sucking  insects  it  is  imperative  that  the 
mixture  come  in  direct  contact  wuth  their  bodies.  Even  a  force- 
ful stream  of  water  from  a  hose  has  often  been  used  to  advantage 
in  disposing  of  aphids  on  cabbage  plants  and  may  also  prove  a 
satisfactory  method  of  getting  rid  of  some  of  the  other  cabbage 
insects. 

The  Cabbage  Plutella. 

Plutella  macuVipennls  Curt. 

Though  not  usually  a  serious  pest,  at  times  the  cabbage  plutella 
causes  considerable  damage  to  the  cabbage  crop  by  eating  small 
holes  through  the  outer  leaves.  The  larvae  are  quite  small  and 
may  easily  be  mistaken  for  young  cabbage  worms :  in  fact,  most 
growers  regard  them  as  the  young  larvae  of  some  other  insect, 
and  the  identity  of  the  cabbage  plutella  is  thus  often  overlooked. 

Description  and  Life  History. — The  larvae  are  generally  more 
abundant  in  a  dry  season  than  in  a  wet  one,  and  there  are  two 
or  three  annual  generations  in  this  part  of  the  countr\',  but  we 
have  not  studied  its  life  history  in  Connecticut. 

Egg. — The  egg  is  white,  very  small  and  generally  attached  to 
the  leaves. 


]6 


CONNECTICUT    EXPERIMENT    STATION    HL'LLETIN    I90. 


Larva. — Pale  green  and  only  about  one- fourth  of  an  inch  long 
when  full  grown.  Very  active,  and  when  disturbed  wriggles  and 
drops  to  the  ground. 

Pupa. — Enclosed  in  a  whitish  open-work  net,  usually  attached 
to  the  leaves.    It  hibernates  in  this  form. 

Adult. — A  small  tineid  moth  having  a  wing-expanse  of  five- 
eighths  of  an  inch,  the  general  color  being  ash-gray  with  light 
clay-yellow  rear  margins  on  the  fore  wings. 

Control  Methods. — The  measures  for  controlling  the  imported 
cabbage  worm  will  also  hold  this  insect  in  check. 

The  Zebra  Caterpillar. 

Mamestra  picta  Harr. 

The  zebra  caterpillar  is  a  very  common  pest  in  the  garden, 
attacking  nearly  all  kinds  of  vegetables  as  well  as  flowering 
plants,  and  is  the  first  insect  recorded  in  this  country  as  feeding 
on  the  beet.  As  a  rule,  in  Connecticut  its  damage  is  not  serious 
or  widespread. 


Fig.  14.     Zebra  Caterpillar,  showing  dorsal 
and  lateral  views.    Natural  size. 


Description  and  Life  History. — A  smooth  caterpillar  about 
two  inches  long  when  full-grown,  and  black  or  dark  brown  strik- 
ingly marked  with  yellow,  as  shown  in  figure  14.  Its  head  is 
orange  or  reddish  yellow.  The  young  caterpillars  feed  in  clusters 
and  may  easily  be  destroyed  by  hand. 

Adult. — The  adult  is  a  noctuid  moth,  having  a  wing-expanse 
of  one  and  one-half  inches,  appearing  in  June.     The  fore  wings 


HARLEQUIN    CABBAGE    BUG.  l^ 

and  thorax  are  reddish  brown  without  prominent  markings.    The 
rear  wings  are  nearly  white,  margined  with  Hght  brown. 

Control  Methods. — Spraying  with  arsenical  poisons  will  con- 
trol this  insect. 

The  imported  cabbage  web-worm,  Hellula  undolis  Fabr.,  and 
the  cross-striped  cabbage  worm,  Evergestis  rimosalis  Guen.,  both 
injure  cabbage  plants  in  the  southern  states  but  are  not  known 
to  occur  in  Connecticut.  The  remedies  used  against  the  other 
cabbage  worms  will  control  them. 

The  Harlequin  Cabbage  Bug. 
Miirganfia  hisfrionica  Hahn. 

The  Harlequin  cabbage  bug  is  a  native  of  ^Mexico  and  Central 
America  and  migrated  into  Texas  about  1864  and  has  gradually 
spread  toward  the  northeast.  It  is  a  serious'  cabbage  pest  in  the 
southern  states  and  even  as  far  north  as  southern  New  Jersey. 
In  1894  it  was  quite  abundant  on  Long  Island  but  Mr.  F.  A. 
Sirrine  whites  that  it  has  not  been  common  there  since ;  and 
that  he  has  not  seen  a  specimen  for  several  years.  The  only 
specimen  thus  far  recorded  from  Connecticut  is  now  in  the  Sta- 
tion Collection,  and  was  collected  at  Meriden,  July  4,  1910,  by 
Mr.  Harry  L.  Johnson.  It  will  probably  never  cause  serious 
damage  in  Connecticut  but  it  is  mentioned  here  so  that  Con- 
necticut growers  may  recognize  it  if  it  appears  in  the  State.  This 
insect  is  also  called  "Calico  Back,"  "Calico  Bug,"  "Terrapin 
Bug,"  and  "Fire-Bug."  It  injures  the  plants  by  sucking  out 
the  sap. 

Description  and  Life  History. — The  eggs  are  barrel-shaped 
and  are  usually  deposited  in  two  rows,  with  one  end  of  each 
egg  fastened  to  the  under  side  of  the  leaf.  They  are  green  at 
first  but  soon  change  to  white  with  black  markings.  Only  two 
or  three  days  are  required  for  hatching'  in  the  southern  states. 

The  nymphs  are  generally  oval  and  somewhat  flattened.  The 
young  are  glossy  yellow,  but  as  they  develop  become  black  with 
reddish  yellow  markings.  In  about  two  weeks  they  become 
mature. 

The  adult  resembles  the  nymph  but  has  wings,  and  is  black 
and  orange-yellow  and  marked  as  shown  in  figure  15.     In  the 


1 8  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

northern  states  the  adults  hibernate  in  rubbish  where  they  can 
find  protection,  but  in  the  south  they  may  be  found  feeding  upon 
cabbage  plants  at  any  time  during  the  winter. 

Control  Methods. — This  "bug"  is  especially  difficult  to  con- 
trol. In  places  where  it  hibernates  all  rubbish  should  be  removed 
from  the  field  in  the  fall,  that  would  furnish  a  place  of  shelter. 
Hand  picking  in  the  early  spring  is  also  effective. 


Fig.  15.     Harlequin  Cabbage  Bug.     Twice  natural  size. 

The  cabbage  flea  beetle,  Phyllotreta  vittata  Fabr.,  which  occurs 
in  Connecticut,  and  the  cabbage  curculio,  Ceutorhynchus  rapcB 
Gyll.,  which  has  not  been  recorded  from  the  state,  are  both 
common  in  New  Jersey  and  feed  on  cabbage  and  allied  plants. 
If  they  should  appear  in  destructive  numbers  in  Connecticut,  a 
spray  of  lead  arsenate  will  probably  serve  to  control  both  insects. 

CUT-AVORMS. 

At  the  Station  farm  in  Mt.  Carmel  in  19 15  considerable  damage 
to  cabbage  plants  was  caused  by  cut-worms.  Many  plants  were 
cut  off  just  above  the  surface  of  the  ground  as  shown  in  figure 
16,  only  a  few  days  after  the  plants  were  set. 

Ordinarily  cut-worms  feed  on  grasses  and  are  not  seriously 
injurious,  but  when  the  field  in  which  they  are  located  is  culti- 
vated, in  the  absence  of  their  natural  food  they  attack  the 
cultivated  crop.  There  are  several  species  of  cut-worms  causing 
similar  damage,  but  the  most  injury  is  done  by  the  common  ones 
and  the  remedy  is  practically  the  same  for  all  species.  These 
cut-worms  are  the  larvae  of  moths  belonging  to  the  family 
Noctuidae.  The  majority  collected  this  season  were  the  so-called 
"well-marked  cut-worm,"   Noctua  clandestina  Harris. 


CUT-WORMS. 


•19 


The  "worms"  feed  at  night,  usually  cutting  off  the  stem  of 
the  plant  just  above  the  ground,  and  go  into  the  ground  to  hide 
during  the  day.  When  full  grown,  in  the  late  spring,  they  are 
of  a  dark  brown  and  blackish  color,  with  stripes  running  longi- 
tudinally.   Usually  there  is  only  one  generation  each  year. 


Fig.  16.     Cut-worm  and  severed  Cabbage  Plant. 
Natural  size. 


The  most  effective  control  method  used  this  season  was  in 
the  form  of  a  sweetened  poisoned  bran  mash.  The  formula  used 
was  that  recommended  for  the  controlling  of  grasshoppers  in 
Kansas,  and  is  as  follows : 

Bran  mash  Yi.  bushel 

Paris  green   I  pound 

Lemons   3 

Molasses   2  quarts 

Water    35^  gallons 

Mix  the  Paris  green  (dry)  with  the  bran  thoroughly.  Squeeze 
the  juice  of  the  lemons  into  the  water  and  cut  up  pulp  and  rind 
into  fine  pieces  and  mix  together.  Then  pour  in  the  molasses 
and  stir.  This  mixture  is  then  added  slowly  to  the  poisoned 
bran  mash  and  when  complete  is  rather  dry  and  easy  to  handle. 
This   should  be  applied  by   scattering  it  broadcast  in   the  late 


20  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    I90. 

afternoon,  if  possible  before  the  plants  are  set,  so  that  it  will 
be  moist  when  the  "worms"  start  to  feed  in  the  early  evening. 
Experiments  have  shown  that  the  use  of  lemons  was  40  per  cent, 
more  effective  than  the  use  of  oranges.  Paris  green  was  also 
found  to  be  more  effective  than  arsenate  of  lead. 

Early  spring  plowing  and  harrowing  will  tend  to  greatly  reduce 
the  number  of  these  "worms."  Trap  crops  are  sometimes  used. 
"Trap  crops  are  those  which  are  planted  as  a  bait  or  lure  to 
attract  the  early  insects  so  that  they  may  be  destroyed  upon  them 
before  the  crop  to  be  protected  is  available." 

Wire-Worms. 

Wire-worms  are  hard,  shiny,  slender,  light  brown  larvae  about 
three-quarters  to  one  inch  in  length,  which  often  bore  into  the 
stems  and  roots  of  many  field  and  garden  crops.  They  belong 
to  the  family  Elateridae,  commonly  known  as  "click-beetles"  or 
"snapping  beetles,"  and  generally  breed  in  sod  ground.  These 
worms  usually  feed  on  the  roots  of  grasses  and  native  plants 
and  are  seldom  noticed.  When  such  ground  is  cultivated  and 
planted  with  vegetables,  the  worms  do  not  have  the  grass  roots 
on  which  to  feed  and  at  once  attack  the  cultivated  crop.  As  it 
takes  from  three  to  five  years  for  these  insects  to  complete  their 
life  cycle,  they  are  a  difficult  pest  to  control.  The  past  season 
there  were  a  great  many  wire-worms  present  at  Wethersfield, 
Connecticut,  and  entirely  ruined  a  crop  of  early  cabbage  at  Fair 
View  Farm,  belonging  to  Mr.  W.  G.  Griswold.  This  form  of 
injury  is  shown  in  figure  17.  At  the  Station  farm  at  Mt.  Carmel 
they  did  considerable  damage  to  lettuce  planted  on  new  ground. 
There  is  no  solution  that  can  be  applied  strong  enough  to  kill 
the  worms  without  injuring  the  plants.  Rotation  of  crops  is 
recommended  and  also  the  placing  of  a  catch-crop. 

Cabbage  Snakes. 

There  are  no  true  snakes  which  infest  cabbages,  but  the  name 
"cabbage  snake"  is  applied  to  a  species  of  Mermis  which  is 
really  a  long,  slender,  cylindrical  worm,  commonly  known  as  a 
"hair  worm"  or  "hair  snake."  These  worms  are  parasitic  in 
the  bodies  of  a  number  of  insects  and  are  often  found  coiled  up 
in  the  soil.     Occasionally  one  is  found  in  a  cabbage  head,  and 


CABBAGE    SNAKES. 


is  made  the  subject  of  a  startling  newspaper  story.     Such  worms 
will  neither  injure  cabbages  nor  persons  eating  cabbages. 


Fig.  17.     Wire-worms  and  Cabbage  Plants  injured  by  them. 
Natural  size. 


One  of  the  "thousand  legs"  (Geophilus  bipwicticeps)  is  also 
found  in  the  heads  of  cabbages  and  is  also  called  a  "cabbage 
snake."  It  is  a  blind,  earth-inhabiting  animal,  is  neither  a  snake 
nor  an  insect,   and  like   the    "hair  worm"    is   not  harmful   to 


cabbages  or  human  beings. 


2  2        connecticut  experiment  station  bulletin  i90. 

Cultural  Practices. 

Truck  crops  in  general  are  peculiarly  susceptible  to  insect 
attack,  there  being  a  total  loss  of  20  per  cent,  of  their  total 
value  due  to  the  ravages  of  insects.  As  many  insects  feed  only 
on  one  crop,  it  is  absolutely  essential  that  the  crops  be  rotated. 
For  example,  the  cabbage  root  maggot  hibernates  in  or  near  the 
field  where  cabbage  has  been  grown,  and  if  that  same  field  is 
planted  to  cabbage  the  next  spring,  food  for  this  insect  will  be 
abundant.  The  result  will  be  a  probable  increase  of  the  pest. 
Crops  such  as  cabbage,  radish,  cauliflower,  etc.,  which  are  closely 
related,  should  be  avoided  in  crop  rotation  as  insects  generally 
feed  on  closely  related  plants. 

Cabbage  stumps,  leaves,  etc.,  should  not  be  allowed  to  remain 
in  the  rows,  but  should  be  removed  from  the  field  and  destroyed 
or  plowed  under  as  soon  as  possible  after  the  crop  is  harvested. 
If  this  is  not  done,  it  leaves  a  hibernating  place  for  insects. 

Late  fall  plowing  destroys  a  great  many  insects  while  hiber- 
nating. Different  insects  pass  the  winter  in  different  stages  of 
development.  Cut-worms  pass  the  winter  in  the  soil  as  larvae, 
while  click-beetles  hibernate  as  newly-formed  beetles.  Cut-worms 
may  be  greatly  reduced  in  numbers  by  early  spring  plowing  and 
harrowing,  which  will  crush  them  or  starve  them  out  before  the 
crop  is  planted. 

Literature. 

The  following  is  a  short  list  of  the  more  important  publications 
treating  of  insects  injurious  to  cabbages : 

Britton  and  Lowry      Report  Conn.  Agr.  Expt.  Station  (Fourteenth  Report 
of  State  Entomologist),  1914,  152. 

Chittenden,  F.  H.        Bull.  19,  N.  S.  Div.  Ent.,  U.  S.  Dept.  Agr.,  1899,  5i. 
Bull.  2.3,  N.  S.  Div.  Ent.,  U.  S.  Dept.  Agr.,  1900,  pp. 

39-50. 
Bull.  33,  N.  S.  Div.  Ent.,  U.  S.  Dept.  Agr.,  1902,  48, 

54,  60,  69,  75-84. 
Cir.  60,  Bur.  Ent.,  U.  S.  Dept.  Agr.,  1905. 
Cir.  63,  Bur.  Ent.,  U.  S.  Dept.  Agr.,  1906. 
"Insects  Injurious  to  Vegetables,"    1907,  131. 

Carman,  H.  Bull.  114,  Ky.  Agr.  Expt.  Station,  June,  1904. 

Bull.  120,  Ky.  Agr.  Expt.  Station,  May,  1905,  78. 

Lowry,  Q.  S.  Report  Conn.   Agr.   Expt.   Station    (Fourteenth   Re- 

port of  State  Entomologist),  1914,  142. 


LITERATURE.  23 

Lugger,  Otto  Bull.  69,  Minnesota  Agr.  Expt.   Station,  Dec,   1900, 

88,  185. 

Quaintance,  A.  L.        Bull.  34,   Florida   Agr.   Expt.   Station,   March,   1896, 
266-286. 

Rumsey  and  Brooks    Bull.  120,  West  Virginia  Agr.  Expt.  Station,  April, 
1909. 

Sanderson,  E.  D.         "Insect  Pests  of  Farm,  Garden  and  Orchard,"   p.  347. 

Schoene,  W.  J.  Bull.  382,  N.  Y.  (Geneva)  Agr.  Expt.  Station,  April, 

1914. 

Sirrine,  F.  A.  Bull.  144,  N.  Y.   (Geneva)  Agr.  Expt.  Station,  Sep- 

tember, 1898. 

Slingerland,  M.  V.       Bull.  78,  Cornell  Univ.  Agr.  Expt.  Station,  1894. 

Smith,  J.  B.  Bull.  200,  N.  J.  Agr.  Expt.  Station,  1907. 

Washburn,  F.  L.  Bull.  100,  Minnesota  Agr.  Expt.  Station,  December, 

1906. 
Twelfth    Report,    Minn.    State    Entomologist,    1907- 
1908,  123,  192. 


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